In the field of microfabrication represented by fabrication of integrated circuit devices by a lithography process, design rules have become more and more minute in order to achieve higher integration. Development of a lithography process enabling microfabrication in a stable manner has been actively pursued.
However, it is difficult to precisely form a fine pattern by a lithography process using KrF or ArF excimer laser beams. For this reason, in order to achieve microfabrication, a lithography process using electron beams in place of KrF or ArF excimer laser beams has been proposed in recent years.
There have been a number of reports disclosing a resist material used for a lithography process using electron beams. Examples of such reports include (1) a positive-tone resist containing a methacryl-main-chain-cut-polymer such as polymethyl methacrylate (PMMA) (for example, refer to Patent Documents 1 and 2), (2) a chemically-amplified positive-tone resist containing a polyhydroxystyrene resin partially protected by an acid-labile group (resin for KrF excimer laser beams), a novolak resin (resin for i-lines), and an acid generator (for example, refer to Non-patent Document 1), (3) a positive-tone and negative-tone resist containing an organic low molecular weight molecule having thin film forming capabilities (amorphous properties) such as calixarene and fullerene (for example, refer to Patent Documents 3 to 11) or a resist using a polyhydric phenol compound (for example, refer to Patent Documents 12 and 13). In addition, a chemically-amplified resist containing 1,3,5-tris[4-(2-t-butoxycarbonyloxy)phenyl]benzene as an organic low molecular weight compound having thin film forming capabilities other than calixarene and fullerene has also been proposed (for example, refer to Non-patent Document 2).    Patent Document 1: JP-A-2000-147777    Patent Document 2: JP-A-11-29612    Patent Document 3: JP-A-11-322656    Patent Document 4: JP-A-11-72916    Patent Document 5: JP-A-9-236919    Patent Document 6: WO 2005/075398    Patent Document 7: JP-A-7-134413    Patent Document 8: JP-A-9-211862    Patent Document 9: JP-A-10-282649    Patent Document 10: JP-A-11-143074    Patent Document 11: JP-A-11-258796    Patent Document 12: JP-A-2006-267996    Patent Document 13: JP-A-2006-235340    Non-patent Document 1: Proc. SPIE. VOL. 5376, 757-764 (2004)    Non-patent Document 2: J. Photo Sci. & Tech. VOL. 12, No. 2, 375-376 (1999)
However, among the above-mentioned electron beam resist materials, the positive-tone resist (1) has problems in etching resistance and sensitivity. It is difficult to use this resist in practice. In order to improve sensitivity, a resist using poly-t-butyl α-chloromethylstyrene or a resin having atoms that makes the resin easily cut by electron beams such as N, O, and S introduced into the terminals have been proposed (Patent Documents 1 and 2). Although a certain degree of improvement in the sensitivity can be seen, the sensitivity and etching resistance of these resins still remain at a level unusable in practice. The chemically-amplified positive-tone resist (2) described in Non-patent Document 1 has high sensitivity. But, due to the use of a resin, the resist has a problem of film surface roughness (hereinafter referred to from time to time as “nano-edge roughness” or “roughness”) when forming minute patterns. The resists (3) using calixarene have excellent etching resistance (for example, Patent Documents 3 to 5). However, these resists have very strong interaction between the molecules due to their structure. Their solubility in a developer is poor and it is difficult to obtain satisfactory patterns. The nano-edge roughness performance of the compound using calixarene derivatives described in Patent Document 6 is not clear.
Even though the resists using fullerene described in Patent Documents 7 to 11 have excellent etching resistance, their coatability and sensitivity are not at a usable level in practice. In addition, the chemically-amplified resist containing 1,3,5-tris[4-(2-t-butoxycarbonyloxy)phenyl]benzene as an organic low molecular weight compound having thin film forming capabilities other than calixarene and fullerene disclosed in Non-patent Document is not sufficient and still needs to be improved in coatability, adhesion to a substrate, and sensitivity in order to become usable in practice. The resists using a polyhydric phenol compound (for example, Patent Documents 12 and 13) exhibit excellent resolution, but their sensitivity is still needs to be improved in order to be used in practice.
The radiation-sensitive compositions disclosed in the Patent Documents 1 to 13 and Non-patent Document 1 and 2 above prior art documents still need to be improved as mentioned above. In addition, none of these compositions can produce a chemically-amplified positive-tone resist film effectively responsive to electron beams or extreme ultraviolet rays, exhibiting excellent resolution, sensitivity, and pattern shape-forming capabilities, and capable of precisely and stably forming fine patterns.
The present invention has been achieved in view of these prior art problems and has an object of providing a compound used as a material for a radiation-sensitive composition capable of forming a chemically-amplified positive-tone resist film which effectively responds to electron beams or extreme ultraviolet rays, exhibits excellent resolution, sensitivity, and pattern shape-forming capabilities, and is capable of precisely and stably forming fine patterns, and a radiation-sensitive composition including the compound.